Analysis of thin impurity doped layers in anodic alumina and anodic tantala films by glow discharge time-of-flight mass spectrometry

The performance of a newly developed pulsed RF glow discharge time-of-flight mass spectrometer (GD TOFMS) in analysis of elemental distributions of impurity species, particularly Cr, B, P, Cl and Cu in anodic film on aluminium and beneath the anodic alumina/aluminium interface and P, B, Cr and H in anodic film on tantalum and beneath the anodic tantala/tantalum interface, with high resolution is presented. The orthogonal TOFMS combined with an appropriate acquisition system enables monitoring of ion signals within the glow discharge period, i.e. during the RF pulse, and within following afterglow, where signals of high intensity, resulting from Penning ionisation, are observed. It was found that GD TOFMS profiling is an extremely powerful and reliable technique for depth profiling analysis that is confirmed from the depth distribution of impurities in the thin, non-conducting, anodic oxide films. The developed configuration allows analysis of layers as thin as 2 nm thickness that are enriched with both positive and negative ions.